The restrictions on in vivo access to the human placenta and the human fetal circulation have resulted in the development of a number of experimental models, which, while extremely useful for some aspects of investigation, fail to represent placental function in vivo adequately. These models can be divided into two types. The first are those, such as the primary cultured trophoblast, which enable specification of precise experimental conditions and allow detailed observation but lack the structural relationships and phenotypic expression of the tissue in vivo. The second are those which retain the structural topology and reflect the effects of the environment in utero, such as the placental in vitro lobule perfusion, but which do not permit manipulation or observation at the cellular level. As more information is obtained concerning molecular and cellular function of the placenta, it is becoming increasingly important to find a way in which processes such as transplacental ion or water transport can be examined in a tissue model to determine how they operate in this more complex, multi-component system. It is necessary therefore to integrate the two model types and develop a new approach in which detailed cellular function can be observed in primary tissue. The goal of this project is to develop a new model, the chorionic villous microperfusion, which will enable these investigations. In this model a small fragment of the chorionic villous tree will be cannulated and perfused through the fetal circulation, while the fragment is simultaneously superfused, simulating the maternal circulation. This will be carried out on the stage of an epifluoresence microscope, enabling observation of fluorescent probes in the syncytial layer or in the fetal vasculature, by devising methods to hold, cannulate and perfuse villous fragments. The second aim is to validate the villous perfusion through measurements of biochemical stability and structural integrity. This model will provide the basis for new investigations in placental transport, metabolism, and signaling and structural biology.